May 13, 2009 -- Scientists say they've devised a risk index that may help predict which people 65 and older are most likely to develop Alzheimer's disease.

The risk index is a 15-point scale, and older people who score an eight or higher are deemed to be at high risk for developing dementia, the researchers report in Neurology.

"The tool could also identify people who have no signs of dementia but should be monitored closely, allowing them to begin treatment as soon as possible and potentially helping them maintain their thinking and memory skills and quality of life longer," says Deborah E. Barnes, PhD, MPH, of the University of California-San Francisco and the San Francisco Veterans Affairs Medical Center.

Some of the items on the risk scale are well-known risk factors for dementia, such as older age, low scores on tests of thinking and memory, and having a gene that's been linked to Alzheimer's.

Other risk factors include being underweight, nondrinkers of alcohol, people who've had bypassheartsurgery, and people who are slow at performing physical tasks, like buttoning a shirt.

Researchers examined 3,375 people, average age 76, with no evidence of dementia and followed them for six years. During that period, 480 people (14%) developed dementia.

Researchers determined which risk factors were best at predicting dementia and created a risk index with points assigned to the risk factors.

Fifty-six percent of those with high scores on the index (eight or more points) developed dementia over the study period, compared to 23% of those with moderate scores (4-7 points), and 4% with low scores (0-3 points).

The index, overall, correctly classified 88% of the participants.

"A late life dementia index could have several important uses," the researchers write. "It could be used to identify high-risk individuals for clinical trials and to target preventions toward those at greatest risk."

It also could be used to identify older adults who should be monitored for symptoms of dementia. And it might be used to reassure people whose risk is considered low or moderate, and give those at high risk information to better prepare them to know when to seek help.